You could change the threshold for a the read to something like 128 or even less as you know that it will be almost 0 when the button is pressed, you can't be sure of the value when the button isn't pressed.

Note that because all of the "switches" will be on until you cover one, you will need diodes on each LDR in order for them to be disambiguated.

Two other things - given that the "on" resistance of the LDR is less than about 7k ohm, which would be less than the effective resistance of the internal pull-ups, you can simply use digital reads and use the internal pull-ups.

Finally, you can "charlieplex" a 4 by 4 keypad if you can wire the keys to suit.

Hi, the only problem I can see is if you have a 4 x 4 array to make sure the shadow of your hand when you cover the LDRs in the centre of the array, you will have to choose your threshold well. Also place a mask over the LDRs so that they have a window over each one,covering the window with your finger will then put the LDR in complete darkness, this will make sure you have a definite covered and uncovered in dull light transition.